The sky is the limit

Oliver Ephgrave speaks to construction experts about China’s plan to build the world’s tallest building in 90 days

In July, Chinese company Broad Sustainable Building (BSB) stunned the construction industry with its audacious proposal to build the world’s tallest building in a mere 90 days. BSB’s proposed Sky City is a 220-storey, 838m-high tower in Changsha, Hunan Province, with construction pencilled to start in November 2012 and finish in January 2013.

The project has reportedly received backing from local authorities, and is pending “final approval from the government”, according to information on the company’s website. BSB claims the secret to building fast lies in its use of its ‘modular technology’, which features “95% factory prefabrication at a five-storey per day construction speed”.

This method was used in the company’s successful construction of a 30-storey hotel in 360 hours in December 2011, following its previous completion of a 15-storey building in six days.

According to Bart Leclercq, head of structures: Middle East at WSP, the engineering firm behind The Shard in London, prefabrication is certainly a concept that makes sense.

“I absolutely love the idea that they are looking at ways to speed up construction. To prefabricate, plan ahead and assemble units before they are hoisted into place and connected together - I think that is innovative. You can see that happening more and more. I think that is brilliant, and I love the ambition.

“From an investor’s point of view, they want to build this as quickly as possible. There are always booms and busts, so I imagine they really want to speed things up [before the next downturn]. BSB has got a lot of people thinking about prefabrication.

It is great, because you are able to manufacture everything under good circumstances in factories. You can make sure the conditions are right, which is difficult on-site. I think that is definitely the way forward.”

Kevin Brass, public affairs manager and journal editor for the Council on Tall Buildings and Urban Habitat (CTBUH), also notes that prefabrication is a method worth exploring more.

“There is a lot of innovation in tall-building design. Prefabrication is not new, but it is an idea worth examining to create an efficient building in more efficient timelines, with fewer materials and at a lower cost. That is really worth taking a look at, especially in China, where there is a huge demand for tall buildings.”

However, Brass adds that building a super-tall tower is very different from a mid-rise tower. “[BSB] has certainly shown it can build quickly, but this new proposal is of a different scale. The prefabrication process and the sheer quantity of materials necessary is a real challenge.

A small building does not prove that they can build at that height.” Leclercq concurs: “By trial and error, it has established that this is quite possible. But do not forget that this is a 220-storey tower - that is no joke.”

After thoroughly scrutinising the details of the Sky City ‘blueprint’ document on BSB’s website, Leclercq highlights the absence of a wind-load strategy. He continues: “What I find strange is they are talking about safety and ‘magnitude nine earthquake resistance’.